Self-Supporting Precast Slab

ABSTRACT

Light, self-supporting precast slab that can be quickly assembled on prefabricated girders of the type used in the construction of viaducts, bridges and similar constructions, characterized by projections located in the bottom part to increase the effective edge, thereby giving the bridge larger spans and enabling the installation inside the girder of conduits or pipes with large diameters, enabling it to be handled and transported by road in compliance with current legislation regulating the transporting of large loads. 
     The present invention contributes the major advantage of providing the bridge with larger spans and the possibility of installing conduits or pipes of a larger diameter than the height of the girder on large bridges or viaducts, thereby enabling it to be fitted quickly and the precast slabs to be safely and simply assembled on the girders, while at the same time reducing the weight of the unit through a reduced cross-section, making it easier to transport and fit.

The present description relates, as its title indicates, to a light, self-supporting precast slab that can be quickly assembled on prefabricated girders of the type used in the construction of viaducts, bridges and similar constructions.

Different types of precast slabs are known at present. In some cases they are conventional precast slabs manufactured on site for their subsequent fitting on girders in bridges or viaducts, their construction and assembly being effected in parts as a period of time must be allowed for the concrete to set.

The precast slabs currently used in projects designed for small bridges or footbridges do not present major drawbacks in relation to the transporting of the prefabricated elements that make up the unit because, as the projects involve small bridges and footbridges, the dimensions of the various elements and prefabricated girders that make up the unit mean they can be handled and transported by road without any great difficulty.

When a large-scale project is engaged in, however, such as large bridges or viaducts where a specific span is also required and the girders must also house conduits or pipes with large diameters, girders with large dimensions are required as the effective edge of conventional precast slabs is not large enough to house conduits with large diameters.

The main drawback involves increasing the dimensions of the girders in order to increase their effective edge and enable the necessary conduits or pipes to be housed, although there is also a problem in terms of the reduction in the span of the bridge in addition to the increase in the weight that the structure has to bear, not to mention an additional transport problem as the legal limits on the size and weight of girders that can be transported by road would be exceeded, bearing in mind that in the majority of cases access to sites is not easy owing to both the roads and the terrain.

Another drawback presented by these girders with large dimensions is that in order to execute the project, and in view of the impossibility of transporting them by road, they have to be constructed on site, with the subsequent increase in costs generated by additional labor, investment in human resources and capital goods and the extension of the time period required to complete the work.

Finally, it should be pointed out that owing to the particular structure of these beams with large dimensions, the fact that they are constructed on site makes them very expensive and difficult to construct due to the quality control that is required for this type of construction.

In order to solve the existing problems, a self-supporting precast slab that is the object of this present invention has been designed, and consists of a light concrete section with cross braces that project out at the bottom and sit on the girders, thereby increasing the effective edge, giving the bridge a large span, and enabling conduits or pipes with large diameters to be installed without the need to resort to the modification of the dimensions of the girders.

The inventive self-supporting precast slab acquires a rectangular form and consists of a light concrete section with the central part being flat and of a smaller thickness, with the lateral sections of both sides being angled slightly upwards, and having at both ends a short perpendicular extension that houses two cross braces, situated at an equidistant distance.

Each brace is provided with two projections that project out of the bottom part of the self-supporting precast slab and are positioned at the ends of the flat area of said precast slab.

The areas of the self-supporting precast slab in which the projections are situated are free of material and consist of sections that adopt the angle of the projection of the braces.

These areas free of material allow the passage of the metallic fastenings that the girders are provided with to ensure the compacting and fixing of the precast slab to the girders at the moment the concrete sets.

This self-supporting precast slab achieves the necessary effective edge for the installation of pipes with large diameters without the need to change the dimensions of the girders thanks to the lower projections with which it is provided.

The self-supporting precast slab can be prefabricated in a single compact block or in various parts, with the correct dimensions as required, so that it can be easily transported by road, thereby complying with current legislation regarding the transporting of large loads.

This self-supporting precast slab for the construction of large bridges or viaducts presented herein contributes numerous advantages over those used at present, the most important of them being, as well as the object of the invention, that the spans of the bridge or viaduct can be increased thereby enabling the conduction of pipes with large dimensions. The effective edge that is required for their installation is achieved by the projections with which it is provided, thus enabling its height to be altered in accordance with the dimensions of the pipe or conduit.

Another important advantage of the present invention is that the effective edge is achieved without the need to vary the dimensions of the girders, thereby reducing the weight the structure has to bear.

We can also cite the added advantage of the assembly between the self-supporting precast slab and the beams, as the precast slab is disposed in its central part with areas free of material, which enable the fastenings of the girders to pass through, thereby enabling their compaction when the concrete sets.

We can also cite the additional advantage that the self-supporting precast slab can be made so it can be installed on single girders or on double or adjoining girders, with only the arrangement and the projections incorporated into the structure of the precast slab varying.

Finally, another added advantage is the reduction in costs resulting from the great ease with which the different parts that make up the girder and the self-supporting precast slab can be assembled.

In order to better understand the object of the present invention, a preferential practical embodiment of said invention has been represented in the plan attached. In said plan:

FIG. 1—shows a perspective of the self-supporting precast slab.

FIG. 2—shows in detail the assembly of a self-supporting precast slab on a single girder.

FIG. 3—shows in detail the assembly of a self-supporting precast slab on double or adjoining girders.

Light, self-supporting precast slab (1) that can be quickly assembled on prefabricated girders of the type used in the construction of viaducts, bridges and similar constructions, which acquires a rectangular form and consists of a light concrete section (2) with the central part (3) being flat and of a smaller thickness, with the lateral sections (4) of both sides being angled slightly upwards, and having at both ends a short perpendicular extension (5) that houses two cross braces (6), situated at an equidistant distance.

Each brace (6) is provided with two projections (7) that project out of the bottom part of the self-supporting precast slab (1) and are positioned at the ends of the flat area (3).

The area of the self-supporting precast slab (1) in which the projections (7) are situated is free of material and consists of sections (8) that adopt the angle of the projection of the braces (7).

These areas free of material allow the passage of the metallic fastenings (9) that the girders (10) are provided with to ensure the compacting and fixing of the precast slab to the girders at the moment the concrete sets.

The self-supporting precast slab (1) achieves the effective edge (11) by means of the projections (7) to enable the installation of pipes with large diameters (12).

Having described the nature of the present invention in sufficient detail, in addition to a means for putting it into practice, all that remains to be added is that its description is not restrictive, and that variations can be made provided that said variations do not alter the essential nature of the characteristics claimed below. 

1. Light, self-supporting precast slab that can be quickly assembled on prefabricated girders of the type used in the construction of viaducts, bridges and similar constructions, thereby providing them with larger spans, characterized in that it achieves the necessary effective edge (11) for the installation of conduits or pipes with large diameters (12) housed in the girders (10), by means of the projections (7) on the braces (6) without the need to change the dimensions of the girders (10).
 2. Self-supporting precast slab according to claim 1 wherein a rectangular base comprises a light concrete section (2), the central part (3) is flat and of a smaller thickness, the lateral sections (4) of both sides are angled slightly upwards, and both ends have a short perpendicular extension (5) that houses two cross braces (6) situated at an equidistant distance.
 3. Self-supporting precast slab according to claim 2 wherein each brace (6) is provided with two projections (7) that project out of a bottom part of the self-supporting precast slab (1) and are positioned between the ends of the flat area (3) and the lateral sections (4).
 4. Self-supporting precast slab according to claim 3 wherein the area of the self-supporting precast slab (1) in which the projections (7) are situated is free of material and comprises sections (8) that adopt the angle of the projection of the braces (7).
 5. Self-supporting precast slab according to claim 3 wherein the area of the self-supporting precast slab (1) in which the projections (7) are situated are free of material and comprises sections (8) that adopt the angle of the projection of the braces (7), housing the metallic fastenings (9) of the girders (10).
 6. Self-supporting precast slab according to claim 1 wherein its structure enables the installation of conduits or pipes with large dimensions without changing the dimensions of the girders, enabling its factory manufacture and subsequent transporting by road, thereby avoiding the need to construct this type of self-supporting precast slab on site, contributing significantly reduced costs in terms of human resources and capital goods.
 7. Self-supporting precast slab according to claim 1 wherein the fact that it can be factory manufactured means all elements can be checked in a rigorous quality control system, thereby assisting with the construction and completion of the site. 